Japanese Utility Model Laying-Open No. 63-89212 (PTD 1) is a prior art document which discloses an ice removing device that removes ice attached to connection terminals connected to a power supply lead. In the ice removing device for a superconducting magnet described in PTD 1, ice is melted by inserting the ice removing device through a connection pipe, and fitting an ice melting portion having a high heat capacity to the connection terminals.